Coaxial cable wound on a drum and process of winding



June 7, 1960 COAXIAL CABLE WOUND ON A DRUM AND PROCESS w. G. HILL2,939,907

OF WINDING Original Filed Feb. 19, 1951 FIG.

Inventor W/LUAM (i. HILL U i e Sm ace COAXIAL CABLE WOUND ON A DRUM AN DPROCESS OF WINDING Claims. cl. 174-113 This invention relates to coaxialconductor cables and.

more particularly to such cables in which the outer conductor is formedby the longitudinal folding of a metal tape into a tube with the edgesof the tape abuttedto, form a seam.

This application is acontinuation of application Ser. No. 211,621, filedFebruary 19, 1951, and abandoned March 29, 1956. v H I In themanufacture of such cables it is the usual prac tice to form a coaxialconductorby passing a conductor having spaced insulating means thereon,horizontally into and through a die, into and through whichis alsopassed a'metal tape which is folded longitudinally .into fa tt'lbefitting over the insulating'menlbers. "The metaltapeis passed intothedie as a fiat-horizontal strip and after magnetic screening tapes and/or binding means have been applied the finished coaxial conductor istaken up on a drum rotating about a horizontal axis, with possibly atake up capstan interposed. The result is that all points of the seam inthe outer conductor lie on radial lines of the take up drum and capstan,the seam facing towards from the axis. In all subsequent operations inmaking up the cable from a coaxial conductor or conductors and otherconductors, the seam remains in the same relation to the axes of thevarious capstans and drums and is thus in the position in which maximumstretching and contracting forces are exerted upon the outer conductortube whenever the coaxial core is flexed on or off the capstan or drum.Similar forces are exerted along a line of the outer conductor tubewhich lies nearest to the surface, of the capstan or drum. The seam isthe weakest part of the tube and thus the usual process of manufacturesuffers from disadvantages.

It has also been found that the outer tubular conductor was liable tokink during the subsequent manufacturing operation, involving bending ofthe coaxial pair, with consequent deterioration of both the uniformityof characteristic impedance and in the dielectric strength.

These disadvantages are removed by the present invention.

In accordance with an aspect of the invention, the tubular outerconductor of a coaxial cable is formed in such way that the abuttingedges of the tubular outer conductor always lie on that diameter of thetubular conductor which is parallel to the axis of the take up drum sothat the seam is in a neutral plane where neither compression nortension is applied to the tube.

The seam remains in the same position relative to the axis about whichthe conductor pair is bent or flexed throughout all the processes up tothe finished cable, which may contain several coaxial conductor pairs,wound on a drum ready for installation. Consequently throughout allthese processes a coaxial conductor pair according to the inventionretains the seam of the outer conductor in the neutral plane.

Experience has confirmed that the side-seam tube is 2 less liable todistortion during the subsequent operations than the. tubes produced bythe known processes. The adoption of the process accordingto thisinvention has led to the production of coaxial conductor pairs whichwill withstand flexing to a greater extent than the previouslyconstructed tubes. Tests have shown that the same amount of flexingwhich reduces the breakdown voltage of a top-seam tube by two thirds andalmost completely disrupts the tube, causes only slight kinking of thesideseam tube and no appreciable diminution of breakdown voltage.

According to a feature of the present invention, there is provided aprocess of manufacturing a coaxial conductor cable which comprises thestep of folding a metal tape longitudinally into a tube with the edgesof the tape abutted together to form a seam, characterized in that thefolding is performed in such relation to the take-up of the folded tubethat the said seam is positioned substantially on the neutral axis ofthe tube as it is wound on the take'=up capstan or drum.

According to another feature of the invention there is provided1 aprocess of manufacturing a coaxial conductor electric cable whichcomprises passing a conductor having spaced insulating members thereonand a metal tape into and through a die to fold the said tapelongitudinally into .a tube fitting over said spacers with and taking upthe coaxial conductors on a take-up drum rotating about an axissubstantially perpendicular to the planein which the-tape passes intosaid die.

The invention will be better understood from the following descriptionof one embodiment thereof taken in conjunction with the accompanyingdrawings in which:

Fig. 1 is an elevation and Fig. 2 a plan of the relevant part of amachine for manufacturing a coaxial core;

Fig. 3 is a cross-section of the coaxial core on the line --a of Fig. 1;

Fig. 4 is a cross section of a cable comprising four coaxial cores.

Referring to the drawings, a central conductor 1 having thereon spacedinsulating discs 2 of polythene is traversed from right to left as seenin the drawings. A metal tape 3 is drawn from a pad 4, over a guideroller 5 and passes through a tool 6 in which the edges of the tape areformed with corrugations in the manner described in British Patent No.668,950, filed February 21, 1950, published July 16, 1952. The tape 3 isthen drawn over a guide roller 7 and turned so that its plane is rotatedthrough into a plane parallel to the plane of the paper. The conductor 1with the discs 2 thereon and the tape 3 are then passed through aforming tool 8 which folds the tape 3 in known manner to form the outerconductor in the form of a tube 9 with the seam 10 formed by theabutting edges of the tape at the side of the core as seen in elevationin Fig. 1. The tube 9 is then traversed past a wrapping head (not shown)by which helical magnetic screening tapes are applied thereto and isthen wound on a take up drum 11 rotated about an axis 12 perpendicularto the plane of Fig. 1 by means not shown. Fig. 3 shows a cross sectionof the coaxial conductor pair consisting of the central conductor '1 andthe outer tube 9 and it will be seen that the seam 10 lies along theneutral axis of the tube 9 with respect to any flexing as it is wound orunwound from the drum 11.

The process above described possesses the further advantage that drossor dirt on the tape 3 will tend to fall away from the tape as the latteris turned into a vertical plane. If desired an air blast may bepositioned to blow on the tape just before it enters the tool 8.

In any subsequent winding of the coaxial core around a drum during theprocesses of making up a cable from the coaxial core the seam 10 willsubstantially maintain Patented June 7, 1960 its relation with respectto the axis about which the core is flexed, since such cores are usuallylaid up by being drawn off floating bobbins and the seam accordinglyremains substantially parallelto the central conductor and in. a'constant relative position inallithe. cores. Fig. 4 shows. a crosssection of. a finished. cable. in which; four coaxial cores 9 are. laidup.together. andwi'th additional:

conductor groups 13 within. an outer leadslieatlitl lland it will beseen that all the. seams preserve thesame re.-.-

lationwith the reel- 15 on.which the,:cable.is wound...

. While the principles of the invention have. been described above. in,connection. with. specific embodiments, and particular.modificationsthereof, it is to .-be. clearly. understood that thisdescription is made only by way of example. and. not: as. a limitationon. the scopeofi the invention.

I claimz. 1.. Anzelectric conductor cable woundonatdrum, com.- prising aplurality of coaxial conductors, the outeri con'-- ductor of each ofsaid coaxial conductors being; in the-- form of. a longitudinally foldedtape'with edgeslabuttingi; to. form asearn', the'seam of eachofasaidouter;conductors. being positioned in the neutral axis oftheouterconductor:

asitliesonthe drum. 2. The cable. according tocIaim. 1i and rounding.said group: ofi'conductorsfon maintaining said relationship; wherebythe: conductors are held-firmly within said jacket withrtheirrneutralaxes fixediin position; 3-. Inxthe processof:manufacturingacoaxialconductor cable: which comprisesfolding ametaltape longitudinally into atube withthe'sedges of'the. tape abutting'to form a.

further. prising means-.for gro'upingsaidplurality. ofconductors'zin a"predetermined relationship, andjacketing: means: sur

abutting together to. form a. seam: and taking up.- the:-

coaxi'allcondilctors on-altal'ce up drum, the. step of'orientingandmaintaining said tube so. that thegseam is. positioned substantiallyon the neutral axis of the tube as it. is'wound on-thedrum: I

5: A process of winding'arr electric cable on. a. drum, the cablecomprising a plurality of coaxial conductors rigidly pnsitioned within acable; jacket, and the-outer conductor of each coaxial conductor beingin the form of a longitudinally" folded tape with edges abutting to forma seam, the process comprising positioning the coaxial conductors sothat the seams thereof are oriented in' the same direction; andwindingthe conductors on said. drum" so that" the seams of the respectiveconductors lie on the'neutral' axesthereofi References-Cited in the fileof this patent UNITED STATES PATENTS 1,975,045 Kossowslrituut Sept. 251934 1 2.1215942. Barrett. June::28,l938? OIH-ER REFERENCES IolinsonsMaterials oi Construction) Sthledition, re

written-by. MLQQ Whithey; and. James Aston, John'Wiley" and-;Sons,.Inc.,.19 18. BirgeaM-Zfirelied upom

